ABSTRACT
We investigate whether there is a variation in the orbital period of the short-period brown dwarf-mass KELT-1 b, which is one of the best candidates to observe orbital decay. We obtain 19 ...high-precision transit light curves of the target using six different telescopes. We add all precise and complete transit light curves from open databases and the literature, as well as the available Transiting Exoplanet Survey Satellite (TESS) observations from sectors 17 and 57, to form a transit timing variation (TTV) diagram spanning more than 10 yr of observations. The analysis of the TTV diagram, however, is inconclusive in terms of a secular or periodic variation, hinting that the system might have synchronized. We update the transit ephemeris and determine an informative lower limit for the reduced tidal quality parameter of its host star of Q$_{\star }^{\prime } \gt (8.5 \pm 3.9) \times 10^{6}$ assuming that the stellar rotation is not yet synchronized. Using our new photometric observations, published light curves, the TESS data, archival radial velocities, and broadband magnitudes, we also update the measured parameters of the system. Our results are in good agreement with those found in previous analyses.
This study investigated the relationship between diabetes (DM) and nitrite, nitrate and MDA levels and effect of melatonin and pentoxifylline.
Sixty mice were randomly divided into four groups. ...Control: no action; Diabetes group (DM): after fasting-blood-glucose (FBG) was measured, 150 mg/kg alloxane was applied intraperitoneally three-times every other day; Diabetes + Melatonin (DM + MLT) and Diabetes + Pentoxifylline groups (DM + PTX): following the same procedures with DM, 10 mg/kg melatonin and 50 mg/kg pentoxifylline were administered subcutaneously six days, respectively. Following FBG analysis, brain tissues were taken under the anaesthesia. Nitrite, nitrate and MDA levels were measured.
In the all groups with alloxane, FBG were higher than in before application (p < .05). Also, FBG, nitrite, nitrate and MDA levels in the DM + MLT and DM + PTX groups were lower than in the DM (p < .05).
Nitrite and nitrate may be related to etiopathogenesis of DM, and pentoxifylline and especially melatonin relatively decrease nitrite, nitrate and lipid peroxidation.
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DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
ABSTRACT
We announce the discovery of GPX-1 b, a transiting brown dwarf with a mass of 19.7 ± 1.6 MJup and a radius of 1.47 ± 0.10 RJup, the first substellar object discovered by the Galactic Plane ...eXoplanet (GPX) survey. The brown dwarf transits a moderately bright (V = 12.3 mag) fast-rotating F-type star with a projected rotational velocity $v\sin {\, i_*}=40\pm 10$ km s−1. We use the isochrone placement algorithm to characterize the host star, which has effective temperature 7000 ± 200 K, mass 1.68 ± 0.10 $\mathrm{\it M}_\odot$, radius 1.56 ± 0.10 $\mathrm{\it R}_\odot$, and approximate age $0.27_{-0.15}^{+0.09}$ Gyr. GPX-1 b has an orbital period of ∼1.75 d and a transit depth of 0.90 ± 0.03 per cent. We describe the GPX transit detection observations, subsequent photometric and speckle-interferometric follow-up observations, and SOPHIE spectroscopic measurements, which allowed us to establish the presence of a substellar object around the host star. GPX-1 was observed at 30-min integrations by TESS in Sector 18, but the data are affected by blending with a 3.4 mag brighter star 42 arcsec away. GPX-1 b is one of about two dozen transiting brown dwarfs known to date, with a mass close to the theoretical brown dwarf/gas giant planet mass transition boundary. Since GPX-1 is a moderately bright and fast-rotating star, it can be followed-up by the means of the Doppler tomography.
In this study, we present spectoscopic observations of the eclipsing binary RR Dra carried out with our recently installed T80 telescope in Ankara University Kreiken Observatory and analyze the first ...radial velocity time series of this system. We simultaneously model TESS light curves along with our radial velocity data to derive absolute parameters of RR Dra system. Additionally, we investigate the period variation of the system using all the available eclipse timings in the literature. In this context, we discuss two possible explanations for the cyclic nature of the eclipse timings: i) light-time effect that corresponds to a high-mass but unseen additional component, ii) magnetic activity of the cooler component. The secular period increase in eclipse timings of RR Dra may be a combination of mass transfer and angular momentum loss, amplified by the presence of circumstellar material.
ABSTRACT
We update the main physical and orbital properties of the transiting hot Saturn planet HAT-P-19 b, based on a global modelling of high-precision transit and occultation light curves, taken ...with ground-based and space telescopes, archive spectra and radial velocity measurements, brightness values from broad-band photometry, and Gaia parallax. We collected 65 light curves by amateur and professional observers, measured mid-transit times, and analysed their differences from calculated transit timings based on reference ephemeris information, which we update as a result. We have not found any periodicity in the residuals of a linear trend, which we attribute to the accumulation of uncertainties in the reference mid-transit time and the orbital period. We comment on the scenarios describing the formation and migration of this hot-Saturn type exoplanet with a bloated atmosphere yet a small core, although it is orbiting a metal-rich (Fe/H = 0.24 dex) host star. Finally, we review the planetary mass–radius, the orbital period–radius, and density, and the stellar metallicity–core mass diagrams, based on the parameters we derive for HAT-P-19 b and those of the other 70 transiting Saturn-mass planets from the NASA Exoplanet Archive.
ABSTRACT
We present broad-band photometry of 30 planetary transits of the ultra-hot-Jupiter KELT-16 b, using five medium-class telescopes. The transits were monitored through standard $B,\, V,\, R,\, ...I$ filters and four were simultaneously observed from different places, for a total of 36 new light curves. We used these new photometric data and those from the TESS space telescope to review the main physical properties of the KELT-16 planetary system. Our results agree with previous measurements but are more precise. We estimated the mid-transit times for each of these transits and combined them with others from the literature to obtain 69 epochs, with a time baseline extending over more than 4 yr, and searched for transit time variations. We found no evidence for a period change, suggesting a lower limit for orbital decay at 8 Myr, with a lower limit on the reduced tidal quality factor of $Q^{\prime }_{\star }\gt (1.9 \pm 0.8) \times 10^5$ with $95{{\rm {per\ cent}}}$ confidence. We built up an observational, low-resolution transmission spectrum of the planet, finding evidence of the presence of optical absorbers, although with a low significance. Using TESS data, we reconstructed the phase curve finding that KELT-16 b has a phase offset of 25.25 ± 14.03 °E, a day- and night-side brightness temperature of 3190 ± 61 K and 2668 ± 56 K, respectively. Finally, we compared the flux ratio of the planet over its star at the TESS and Spitzer wavelengths with theoretical emission spectra, finding evidence of a temperature inversion in the planet’s atmosphere, the chemical composition of which is preferably oxygen-rich rather than carbon-rich.
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